High-voltage distribution cabinet
Electrical products for power system generation
High-voltage distribution cabinets refer to electrical products used in power systems for generation, transmission, distribution, energy conversion, and consumption, which perform functions such as switching, control, or protection. These products operate at voltage levels between 3.6kV and 550kV and mainly include high-voltage circuit breakers, high-voltage disconnectors and earthing switches, high-voltage load switches, high-voltage automatic reclosing and sectioning devices, high-voltage operating mechanisms, high-voltage explosion-proof distribution units, and high-voltage switchgear cabinets. The high-voltage switch manufacturing industry is a crucial part of the power transmission and transformation equipment manufacturing sector, holding a very significant position in the entire power industry.
Feature
The distribution cabinet features overhead incoming and outgoing lines, cable incoming and outgoing lines, and busbar interconnection functions.
Composition
The distribution cabinet should meet the requirements of GB3906-1991 "3-35 kV AC metal-enclosed switchgear," consisting of two main parts: the cabinet and the circuit breaker. The cabinet is composed of the shell, electrical components (including insulating parts), various mechanisms, secondary terminals, and wiring, etc.
Cabinet Material
1) Cold-rolled steel plates or angle iron (for welding cabinets)
2) Aluminum-zinc coated steel sheets or galvanized steel sheets (for cabinet assembly)
3) Stainless Steel Sheet (Non-magnetic)
4) Aluminum Sheet (Non-magnetic)
Functional Unit
1) Main Busbar Room (the general arrangement of main busbars is typically in a "crane" or "1" shape structure)
2) Circuit Breaker Room
3) Cable Room
4) Relays and Control Panels
5) Busbar Compartment on the Top of the Cabinet
6) Secondary Terminal Compartment
Cabinet Components
Common one-time electrical components (main circuit equipment) used inside cabinets include the following equipment:
Current Transformer, abbreviated as CT [e.g., LZZBJ9-10]
Voltage Transformer, abbreviated as PT [e.g., JDZJ-10]
Zero-sequence Current Transformer
Circuit Breaker Cabinet
Grounding Switch [e.g., JN15-12]
Surge Protectors (Capacitive Reactors) [e.g., Single-phase type HY5WS; TBP, JBP Combination Type]
Isolation Switches [e.g., GN19-12, GN30-12, GN25-12]
High-voltage Circuit Breakers [such as: Low-oil Type (S), Vacuum Type (Z), SF6 Type (L)]
High Voltage Contactor [e.g., Type JCZ3-10D/400A]
High-voltage Fuse [e.g., RN2-12, XRNP-12, RN1-12]
Transformers [e.g., SC(L) Series Dry Transformers, S Series Oil Transformers]
High-Voltage Live Display [DXN-Q Model, DXN-T Model]
Insulating Components [e.g., wall penetration sleeves, terminal boxes, insulators, insulated heat shrink (cold shrink) sleeves]
Main busbar and branch busbar
High-voltage reactors [such as series type: CKSC and starting motor type: QKSG]
Load Break Switch [e.g., FN26-12(L), FN16-12(Z)]
High-voltage single-phase parallel capacitors [such as: BFF12-30-1] etc.
2. Major secondary components commonly used within cabinets (also known as secondary equipment or auxiliary equipment, which refers to low-voltage equipment used for monitoring, controlling, measuring, adjusting, and protecting primary equipment), including the following equipment:
Relays, watt-hour meters, ammeters, voltmeters, power meters, power factor meters, frequency meters, fuses, circuit breakers, changeover switches, signal lights, resistors, buttons, microcomputer comprehensive protection devices, etc.
Categories
Toggle switch
Circuit breakers are categorized by installation type into withdrawable (pulled out) and fixed styles.
(1) Removable or Handcart Type (denoted by Y): Indicates that the main electrical components (such as circuit breakers) inside the cabinet are mounted on a removable handcart. Due to the excellent interchangeability of the handcart cabinet, it can significantly enhance the reliability of power supply. Common handcart types include: isolation handcart, metering handcart, circuit breaker handcart, PT handcart, capacitor handcart, and transformer handcart, etc., such as KYN28A-12.
(2) Fixed-Type (represented by G): Indicates that all electrical components inside the cabinet (such as circuit breakers or load switches, etc.) are fixed-type installations. Fixed-type switch cabinets are more simple and cost-effective, such as XGN2-10, GG-1A, and so on.
By location
Indoor and outdoor, categorized by installation location
(1) For Indoor Use (denoted as N); indicates that it is only for installation and use indoors, such as: KYN28A-12 switchgear, etc.
(2) For Outdoor Use (indicated by "W"); denotes that the product can be installed and used outdoors, such as: XLW switch cabinets.
By cabinet structure
Switchgear cabinets can be categorized into four main types: metal-enclosed armored switchgear, metal-enclosed partitioned switchgear, metal-enclosed box-type switchgear, and open-type switchgear.
Metal-enclosed armored switchgear (represented by letter K) mainly consists of components such as circuit breakers, transformers, busbars, etc., which are individually housed in metal-enclosed switchgear within compartments separated by grounded metal partitions. For example, the KYN28A-12 type high-voltage switchgear.
(2) The Metal-Enclosed Switchgear with Segregated Compartment (represented by letter J) is similar to armored metal-enclosed switchgear. Its main electrical components are also separately mounted in individual compartments, but it features one or more non-metallic partitions that meet certain protection levels. For example, the JYN2-12 type high-voltage switchgear.
(3) Metal-enclosed switchgear cabinets (represented by the letter X) are switchgear devices with metal encased cabinets. For example, the XGN2-12 type high-voltage switchgear cabinet.
(4) Open-type switchgear, no protection grade required, with a portion of the casing being an exposed switchgear. Such as the GG-1A(F) type high-voltage switchgear [2].
Five Precautions
1. The vacuum circuit breaker carriage within the high-voltage distribution cabinet fails to reach the working position after closing at the test location. (Prevents incorrect opening and closing of circuit breakers)
2. The grounding switch within the high-voltage distribution cabinet cannot be engaged when the carriage circuit breaker is in the closed position. (To prevent engagement with the grounding wire)
3. During the closing operation of the vacuum circuit breaker within the high-voltage distribution cabinet, the cabinet door is locked using the mechanical device on the grounding switch, securing it to the back door of the panel. (To prevent accidental entry into the live compartment.)
4. The vacuum circuit breaker inside the high-voltage distribution cabinet fails to close during operation, and the grounding switch cannot be engaged. (To prevent live-line grounding)
5. The vacuum circuit breaker within the high-voltage distribution cabinet cannot be withdrawn from the trolley circuit breaker's operating position during the closing and operation phase (to prevent opening the switch with load).
Relevant standards
SJ/T 31401-1994 | Requirements and Inspection and Evaluation Methods for High-Voltage Switchgear Cabinets
DL/T 791-2001 | Guidelines for Selection of Indoor AC Filled-type Switchgear
DL 404-1991 | Indoor AC High-Voltage Switchgear Ordering Technical Specifications
DL/T 404-1997 | Indoor AC High-Voltage Switchgear Ordering Technical Specifications
DL/T 539-1993 | Indoor AC High-Voltage Switchgear and Components - Technical Conditions for Dew Condensation and Pollution Tests
TB/T 2010-1987 | 27.5kV AC Electrified Railway Switchgear Technical Conditions
DL/T 404-2005 | Indoor AC High-Voltage Switchgear Procurement Technical Conditions [1]
Product Model and Its Meaning
Usage
1. KYN-10 Indoor AC Metal Armored Draw-out Switchgear (hereinafter referred to as the handcart cabinet) is suitable for indoor complete power distribution systems with a single-phase or single-phase segmented system, rated voltage of 3-10KV, 50Hz AC frequency, and center point not grounded. It is used by various types of power plants, substation, and industrial and mining enterprises for receiving and distributing network power, and for controlling, protecting, and monitoring the circuit.
2. The KYN-(F-C) indoor armored double-layer open switchgear for 3.6~12kV three-phase AC 50Hz, single bus and single bus section systems is a complete indoor switchgear. It is primarily used as a high-voltage distribution device in power plants, sub-stations, metallurgy, papermaking, petrochemical, textile, and industrial and mining enterprises. It is suitable for the control and protection of motors, transformers, and capacitors.
3. The KYN-12/1250-31.5 indoor armored withdrawable AC metal-enclosed switchgear is referred to as a switch, which is a complete power distribution system for 3.6-12KV, three-phase AC 50Hz single busbar and single busbar sectioning systems. It is mainly used for power plants, transmission of electricity from small and medium-sized generators, distribution in industrial and mining enterprises, and receiving and transmitting electricity in the secondary substation of the power industry system, as well as for starting large high-voltage motors, etc. It is used for control, protection, and monitoring. This switchgear meets the requirements of IEC298, GB3906, and other standards.
Structural Features
1. The KYN indoor AC metal-enclosed switchgear (hereinafter referred to as the "handcart cabinet") is designed and manufactured in accordance with the "3-35KV AC metal-enclosed switchgear" standard and IEC298 "AC metal-enclosed switchgear and control equipment" standard. It also meets the requirements of the Ministry of Water Resources for high-voltage switchgear to have "five prevention" functions.
2. The KYN-(F-C) indoor armored double-layer switchgear is a component of the KYN-(F-C) indoor armored double-layer switchgear, which can be used in conjunction with the KYN-(F-C) indoor armored double-layer switchgear to form a modular distribution unit. This switch cabinet is a double-layer armored F-C cabinet, with one cabinet capable of housing two F-C switchboards, equivalent to the functionality of two single-layer cabinets, while occupying approximately the same space as a single-layer cabinet. It saves a significant amount of floor space and equipment investment for users. This product features a vacuum contactor specifically designed for double-layer cabinet structures, offering simple design, compact size, attractive appearance, high insulation level, and long lifespan. It comes with both electrical retention and mechanical locking mechanisms.
3. KYN-12/1250-31.5 Indoor Armored Withdrawable AC Metal Enclosed Switchgear, featuring an armored cabinet structure with a central arrangement, divided into the breaker room, main busbar room, cable room, and relay instrument room. To enable the cabinet to withstand internal fault arcs, exhaust ducts and pressure relief windows are provided in all functional compartments except the relay room. The primary contacts are bundled round terminals.
Switches can be high-availability as per customer requirements, featuring a front-maintenance structure for wall-mounted or back-to-back installation. The switch equipment is equipped with a safe and reliable interlock mechanism, fully meeting the "Five Preventive" locking requirements.
a, The circuit breaker's handcart cannot close during the pushing or pulling process.
b, The circuit breaker's handcart can only be operated for closing and opening when it is in the test position or working position, and the handcart cannot be pulled out from the working position when the circuit breaker is closed.
c, The circuit breaker drawer can only be moved from the test position to the operating position when the earthing switch is in the open position; the earthing switch can only be operated to open or close when the circuit breaker drawer is in the test position or outside the cabinet.
d, The back door cannot be opened when the grounding switch is in the open position.
e, When the handcart is in the working position, the secondary plug is locked and cannot be removed.
The base frame of the circuit breaker room, aside from having fixed guide rails for the movement of the handcart, also features extendable guide rails on both sides of the fixed guide rails for easy observation and inspection of the circuit breakers. After the circuit breaker is disconnected, the two extendable guide rails can be pulled out to the outside of the cabinet, allowing the handcart to be directly moved from inside the cabinet to the extended guide rails outside.
Please include some high-pressure cabinets that are available in the market:
① GR Series:
Application
The GRC1 type high-voltage distribution cabinet is used in 3~10kV substation to improve the power factor of the power grid. This series of cabinets consists of a capacitor cabinet, a transformer cabinet, and a measurement and discharge cabinet.
Solution Categories
The GRC1 model is a standard type, consisting of a capacitor cabinet and a transformer cabinet. The capacitor cabinet comes in four configurations, while the transformer cabinet offers three options.
2. The GRC1C model is a horizontal differential protection type, meaning that when a capacitor in the cabinet trips, the main circuit breaker trips due to the current transformer driving the cross differential circuit. This model also has four options.
3. The GRC1Y type is an inductor-type reactor, which is a capacitor cabinet equipped with a series reactor to suppress higher harmonics.
Structure
The cabinet is made of angle steel and thin steel plates, bent and welded together in three layers. The bottom layer features an oil trough panel and a measurement and discharge cabinet. Voltage transformers are placed in the middle layer, while reactors are installed in the bottom layer. The front is a steel plate door, which can accommodate instruments, switches, and signal lights.
②GGX2 Series:
Usage
The GGX2C10 high-voltage vacuum circuit breaker is suitable for a three-phase AC power grid with rated voltage of 3~10kV and frequency of 50Hz. It serves as a complete distribution system for receiving and distributing electrical energy, as well as for controlling, monitoring, and protecting the circuit.
Structural Features
This power distribution cabinet features a metal-enclosed box-type housing, with all live parts enclosed inside and segmented into busbar room, circuit breaker room, cable room, and a separate instrument box structure mounted on the cabinet; vacuum circuit breakers and electromagnetic or spring-operated mechanisms are an integrated unitized structure, which is fixed inside the cabinet with bolts after insertion. There are 24 main wiring schemes.
③ GGX2 Series:
Usage
The GSGC1A type double busbar high-voltage switchgear is suitable for regional sub-stations, large-scale industrial and mining enterprise sub-stations, and electrical equipment test stations with voltages of 3, 6, 10kV, AC 50Hz double busbar systems. It can also be used in power supply systems with a single busbar and a bypass busbar for the purpose of receiving and distributing electrical energy.
Structure
The cabinet is constructed from thin steel plates and angle iron welded together, with the base made of channel steel. The front features a single-panel security door, while the back has a double-panel security door. The busbars on top are exposed.
The cabinet is divided into two compartments, the front compartment equipped with a spare (starting) busbar isolator switch, circuit isolator switches, cable heads, etc., with a spare (starting) busbar mounted at the top. The rear compartment contains the main (operational) busbar isolator switch, oil circuit breakers, and a main (operational) busbar isolator switch at the top. Current transformers can be installed below the compartments. The operating mechanisms for the oil circuit breakers and isolator switches are mounted on the front of the cabinet. A single-panel steel door is located on the left rear of the cabinet, leading to the relay room. Thin steel plates separate the compartments and primary from secondary electrical equipment. Maintenance of secondary electrical equipment can be performed without interrupting power to the primary equipment.
To prevent accidental operation by staff, the cabinet is equipped with a programmed electrical interlock device.
Electrical Indicator Device
I. Analysis of Issues with High-Voltage Distribution Cabinets
(1) The function of the high-voltage distribution cabinet preventing accidental entry into the live compartment causes the opening and closing of the switchgear door to be interlocked with the grounding switch. That is, the switchgear door can only be opened after the grounding switch is closed. This incident has exposed the imperfect issue of the mechanical interlock device for the "Five Preventions" in the old model high-voltage switchgear.
(2) The issue of voltage verification for high-voltage distribution cabinets has been a long-standing concern in power safety production. The currently promoted fully enclosed "Five Preventive Measures" switchgear with mechanical "Five Preventive Measures" locking devices fails to meet the safety regulation requirement of "verify voltage first, then connect the grounding wire." This is because during the execution of power-off work, it is necessary to verify that the equipment is voltage-free before closing the grounding switch. However, the fully enclosed high-voltage switchgear is in a fully sealed state. According to normal operation procedures, it is impossible to verify the voltage of the equipment using a portable high-voltage voltage tester. Consequently, a method of forcibly unlocking and opening the switchgear door to verify the voltage has emerged.
(3) A large number of high-voltage live indicator devices using neon lamps as display elements were installed on the distribution cabinets. After long-term operation, a high failure rate and extensive damage to neon bulbs were observed. To address this缺陷, a neon lamp on/off switch was installed on the live indicator device. Normally, this switch is kept off, temporarily shutting down the entire high-voltage live indicator device. This approach, however, negates the device's function of monitoring the live status of the line side.
(4) Neon lights have low brightness, especially in bright environments where the brightness is washed out, resulting in poor visibility.
(5) Outdated high-voltage live display units equipped with mandatory electrical interlock, featuring a simplistic locking principle. They merely half-wave rectify the signals from the A, B, and C phase sensors and combine them directly to control the interlock circuit. This method, however, can lead to malfunctions when the system encounters abnormal conditions such as single-phase grounding or phase loss, as the fluctuation in the interlock control voltage can cause the unit to fail to reliably lock, potentially resulting in an accident where a live switch is closed to ground.
(6) Neon-lamp type high-voltage energized display devices installed usually have plastic casings and are mounted within high-voltage equipment compartments. In the event of an internal short circuit arc in the switchgear during operation, the high-temperature arc may melt the plastic casing of the device, potentially injuring operators or maintenance personnel.
Part Two: Solutions to Existing Issues
Due to the numerous issues with old-style high-voltage live indicator devices, there is an objective need for a new type of live indicator with high reliability, long lifespan, no maintenance required, clear and prominent display, and the ability to compensate for the deficiencies of the old-style high-voltage live indicator devices. The Beijing Power Supply Bureau has successfully developed a new high-voltage live indicator verification device. When used with the CG series sensors, this device displays live status and verifies live voltage on-site, indicating whether high-voltage equipment is running at voltage levels and features electrical interlock functionality. This device resolves many issues with neon lamp live indicator devices, with its dual display consisting of a liquid crystal display and a long-life flash verification plug, which is suitable for operation under various light conditions and is highly visible. A dedicated verification plug is designed to provide a unique removable independent verification function, enhancing the device's reliability as a verification basis. The device employs phase-detection digital superposition interlock control technology, ensuring that the interlock voltage remains constant and stable during abnormal operations such as phase loss. The mandatory electrical interlock function can reliably lock out ground switches (cabinet doors). The application of the new high-voltage live indicator verification device effectively prevents accidents caused by mistakenly entering live spaces or closing live switches to ground, thus protecting both personnel and equipment.
Safety is the foundation of power generation, and prevention is the key to ensuring safe production. In the current safety and production of power, electric shock accidents and mishandling incidents are still the two major threats to safe production. Continuously improving and refining technical measures to prevent electric shock accidents and mishandling incidents is the goal that every employee in the power industry should strive to achieve.
